Logfile的不同状态

一、  V$LOG:STATUS 指的是GROUP的状态

UNUSED：

尚未记录change的空白group（一般会出现在，loggroup刚刚被添加，或者刚刚使用了resetlogs打开数据库，或者使用clear logfile后）

CURRENT:

当前正在被LGWR使用的group(同时是ACTIVE状态)

ACTIVE：

未被LGWR写，instance recovery需要的。还没有完成checkpoint。

INACTIVE：

online,未被LGWR写，对instance recovery不再有用了。

CLEARING：

正在被clear的group（Log is being re-created as an empty log after an ALTER DATABASE CLEAR LOGFILE statement. After the log is cleared, the status changes to UNUSED.）

CLEARING_CURRENT:

一个正在被clear的CURRENT group（Current log is being cleared of a closed thread. The log can stay in this status if there is some failure in the switch such as an I/O error writing the new log header.）出现在中状态一般是有错误的。

二、V$LOGFILE:STATUS指的是member的状态

INVALID:

             不能使用的member,可能损坏了(另外，刚加入到redolog group的日志文件在被使用之前也是这个状态)

STALE：

            见下面解释

DELETED：

      被alter database drop logfile member的member

BLANK:

            正常的都是blank，不管是否被写。

下面是对metalink上对stale的解释：

Log files may have a status of stale regardless of redo log mirroring or

archival mode.

Solution Description:

=====================

In general, the stale status of a redo log member should not be a cause for

great concern, unless you observe that this happens frequently or

systematically.  Keep in mind that a stale log is not necessarily an invalid

log, but more of an "in-doubt" one. Once the corresponding redo group becomes

the current one again, the stale status will go away by itself.

下面是一个例子：

logfile中有两个file为stale状态，当发生日志切换时，group1变成current状态，从而，group1下的logfile变成

blank(正常状态)

另外，这个例子也展示了logfile group从active到inactive的变化。

当发生switch logfile前，group5为current状态，switch logfile后，group5变为active状态，这说明recovery时

group5是有用的，同时也说明logfile时发生的不是完全检查点。

当手工发生检查点后，group5从active变为了inactive状态，此时，group5对recovery不再有用。这说明：

alter system checkpoint发生的是完全检查点。

SQL> l  

  1* select * from v$logfile

SQL> /

    GROUP# STATUS  TYPE    MEMBER

---------- ------- ------- ----------------------------------------

         1 STALE   ONLINE  /opt/oracle/oradata/userlog2/redo01.log

         2 STALE   ONLINE  /opt/oracle/oradata/userlog2/redo02.log

         3         ONLINE  /opt/oracle/oradata/userlog2/redo03.log

         4         ONLINE  /opt/oracle/oradata/userlog2/redo04.log

         5         ONLINE  /opt/oracle/oradata/userlog2/redo05.log

SQL> select * from v$log;

    GROUP#    THREAD#  SEQUENCE#      BYTES    MEMBERS ARC STATUS           FIRST_CHANGE# FIRST_TIM

---------- ---------- ---------- ---------- ---------- --- ---------------- ------------- ---------

         1          1         21   20971520          1 NO  INACTIVE                704228 07-AUG-06

         2          1         22   20971520          1 NO  INACTIVE                753376 07-AUG-06

         3          1         23   20971520          1 NO  INACTIVE                785843 07-AUG-06

         4          1         24   20971520          1 NO  INACTIVE                868923 08-AUG-06

         5          1         25   20971520          1 NO  CURRENT                 951980 10-AUG-06

SQL> alter system switch logfile;

System altered.

SQL> select * from v$logfile;

    GROUP# STATUS  TYPE    MEMBER

---------- ------- ------- ----------------------------------------

         1         ONLINE  /opt/oracle/oradata/userlog2/redo01.log

         2 STALE   ONLINE  /opt/oracle/oradata/userlog2/redo02.log

         3         ONLINE  /opt/oracle/oradata/userlog2/redo03.log

         4         ONLINE  /opt/oracle/oradata/userlog2/redo04.log

         5         ONLINE  /opt/oracle/oradata/userlog2/redo05.log

SQL> select * from v$log;

    GROUP#    THREAD#  SEQUENCE#      BYTES    MEMBERS ARC STATUS           FIRST_CHANGE# FIRST_TIM

---------- ---------- ---------- ---------- ---------- --- ---------------- ------------- ---------

         1          1         26   20971520          1 NO  CURRENT                 994126 10-AUG-06

         2          1         22   20971520          1 NO  INACTIVE                753376 07-AUG-06

         3          1         23   20971520          1 NO  INACTIVE                785843 07-AUG-06

         4          1         24   20971520          1 NO  INACTIVE                868923 08-AUG-06

         5          1         25   20971520          1 NO  ACTIVE                  951980 10-AUG-06

SQL>

SQL> alter system checkpoint;

System altered.

SQL> select * from v$log;

    GROUP#    THREAD#  SEQUENCE#      BYTES    MEMBERS ARC STATUS           FIRST_CHANGE# FIRST_TIM

---------- ---------- ---------- ---------- ---------- --- ---------------- ------------- ---------

         1          1         26   20971520          1 NO  CURRENT                 994126 10-AUG-06

         2          1         22   20971520          1 NO  INACTIVE                753376 07-AUG-06

         3          1         23   20971520          1 NO  INACTIVE                785843 07-AUG-06

         4          1         24   20971520          1 NO  INACTIVE                868923 08-AUG-06

         5          1         25   20971520          1 NO  INACTIVE                951980 10-AUG-06

  - The End-